Traveling wave electron discharge device



Oct. 4, 1960 11.1. MARCHESE TRAVELING wAvE ELEcTRoN DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed Jan. 16. 1958 Inventor THEODRE J NC//SE By Wow Agent Oct. 4, 1960 T. J.'MARCHESE TRAVELING wm: ELECTRON DISCHARGE DEVICE File-d Jan. 16. 1958 2 Sheets-Sheet 2 Inventor 7/1E0O0RE L. MARCHESE B, @New Agent v m Q United States atent O TRAVELING WAVE ELECTRON DISCHARGE DEVICE 'I'heodore J. Marchese, Nutley, NJ., assigner to International Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Maryland Filed Jan. 16, 1958, Ser. No. 709,368

24 Claims. (Cl. S15-3.5)

This invention relates to traveling wave electron discharge devices and more particularly to broadband radio frequency impedance matching devices to provide a substantially reflectionless impedance transformation between relatively high impedance propagating structures, such as a helical propagating structure, and relatively low impedance input and output radio frequency transmission lines usually employed in such discharge devices.

One of the problems in the helix type of traveling wave tube is in obtaining a broadband impedance match between radio frequency transmission lines and the helical wave propagating structure. A helix type of traveling wave tube may have a useful operating frequency range of over 2 to l, with the useful range limited by the quality of the radio frequency impedance match. It is known that to cover a 2 to l or greater `operating frequency range, coaxial line radio frequency circuit connections are usually resorted to since waveguide transmission lines have well known bandwidth limitations. The characteristie impedance of coaxial lines may be in the order of 50 ohms, while the circuit impedance lof traveling wave tube helices may be in the order of several hundred ohms. There is then, clearly, the problem of matching -a low impedance coaxial radio frequency line to a helical radio frequency line of a much higher impedance than the coaxial line.

There are a number of different types of impedance that the impedance between the helix and the ground sleeve is in the order of the impedance of the coaxial transmission line, thereby enabling la direct connection between the helix and the coaxial transmission line. In other applications, this helix-above-ground plane impedance transformation cannot be carried to the extent that the impedance between the helix and the ground plane is reduced to that of the impedance of the coaxial transmission line. This necessitates the necessity of incorporating a tapered transformer arrangement in the coaxial transmission line. At the lower frequencies, there often is not room enough for this type of transformer in the coaxial line. Therefore, other arrangements have to be resorted to. v

An object of this invention is the provision of means to provide a useful operating frequency range for a helix type of traveling wave tube of over 2 to l.

Another object of this invention is to provide an improved means for matching a low impedance radio frequency 4line to a high impedance wave energy propagating line of helical configuration. Y

A feature of this invention is vthe provision of abroadband radio frequency impedance matching device for use between a relatively low impedance wave energy propagating line and a relatively high impedance wave ,energy propagating line comprising a spiral conductor and a rice 2 ground conductor disposed in tapered spaced relationship.

Another feature of this invention is the provision lof a broadband radio frequency impedance matching device for use between a relatively low impedance wave energy propagating line and a relatively high impedance wave energy propagating line comprising in combination lirst and second impedance transition sections `and means coupling equal impedance points tof said first and second transition sections to each other. The rst transition section is characterized by including a conducting cylinder and a helical conductor disposed within and coaxially of said cylinder, the spacing between said conducting cylinder and said helical conductor being tapered from a narrow spacing to a relatively wide spacing and said second transition section is characterized by including a spiral conductor and a conductive surface disposed in tapered spaced relation.

Still another feature of this invention is the configuration of the secondl transition section of the impedance matching arrangement lof this invention which includes a conductive disk disposed coaxially of and extending radially from a given axis and a conductive spiral disposed coaxially of said given axis 'and in tapered spaced relationship with respect to one of the planar surfaces of said disk.

A further feature of this invention is the provision-of the second transition section of the impedance matching arrangement of this invention having the configuration including a conductive cylinder and a conductive spiral disposed within and coaxially of and extending along the longitudinal axis of said conductive cylinder in tapered spaced relationship with the inner surface of said con,- ductive cylinder.

Still a further feature of this invention is the provision of the'second section of the impedance matching device of this invention wherein the input second transition section lis a spiral conductor disposed in tapered spaced re- Vlationship with one planar or ground surface of a disk extending radially from and coaxial of the axis of the propagating structure .of a traveling wave tube, and the output second transition section is a spiral conducto-r disposed in tapered spaced relationship with the other `planar for ground surface of the same disk, and means are provided to couple the `second transition section to the rst transition Asection of the input and output impedance matching devices.

The above mentioned and other features and Qblccts .of this invention will become more apparent by reference tothe following description taken in conjunction with the `acompanying drawings, in which:

Fig. 1 is a ,cross-,sectional view of a traveling wave tube illustrating an impedance matching device following the principles of this invention;

Fig. 2 isa `cross-sectional view taken along line 2 2 of Fig. l;

Fig. 3 is a cross-sectional view of an alternative arrangement of the impedance matching device illustrated .inFia 1;

. Fig. .4 vis a cross-sectional view of 'another embodiment of vthe impedance matching device following the prin- .ciples of this invention;

Fig. 5 is a crossfsectional `viewof a traveling wave v electron discharge deviceillustrating still another form that the impedance matching device of this invention may take; `and l Fig. 6 is across-sectional view of a traveling wave electron discharge device incorporating still another form of impedance matching device following the principles of lthis invention.

Referring ,to Fig. l, .a traveling wave tube is illustrated in conjunction With one forrn of impedance `matching device following the principles of this invention. The

traveling wave tube is illustrated as including an envelope 1 including therein an electron gun 2 to project an electron beam along a given path to collector electrode 3; Disposed in interacting .relation withtheelectrons of the electron beam 'is apropagating'structure 4 wherein Vamplification of waveenergy takes place through the interaction with the electrons of theelectr'onbeam. As is wellV known, the wave energy Vto be amplied may becoupled to the input of the traveling wave tube by a coaxial transmission line 5, and the ampliiied wave energy may be coupled from the output of the propagatingfstructure- 4 by means of coaxial transmission line 6. To assure a broadband reilectionless ampliiication of the wave energy in the traveling wave tube, it is necessary to match the relatively low impedance of therinput and Voutput lines 5 and 6 to the relatively high impedance at the input and output ends 7 Vand 8, respectively, of helical propagating structure 4.

` In accordance with this invention, the impedance match Yto provide this reectionless coupling of energy at the input end of propagating structure 4 is accomplished by employing a rst transition section 9 and a second transition section '10. The first transition 9 includes a conducting cylinder 11 coaxial of the axis of the helical propagating structure 4 and Ya helical conductor 12 disposed coextensive with and within and coaxial of, cylinder 11. As will be noted, helical conductor 12 is coupled to the input end of propagating structure 4 and is aligned along the axis thereof. It will be further noted that cylinder 11 is 'characterized by three portions, portion 13 providing a relatively vwide spacing between cylinder 11 and helical conductor 12, portion 14 providing a relatively narrow spacing between cylinder 11 and helical conductor 12 and a tapered portion 15 which gradually varies the spacing between cylinder 11 and the conducting helix 12 between portions 13 and 14.v With this arrangement the impedance of the rst transition section 9 in theV vicinity of portion 13 of cylinder 11 is substantially equal to the characteristic impedance of propagating structure 4. The tapered section 15 gradually reduces this impedance to a value intermediate the relatively high' impedance of propagating structure 4 and the relatively low impedance of the coaxial: transmission line 5.

An extension of helical conductor 12 provides an electrical connection between transition section 9 and `transiplanar ground conductor 2!) as illustrated. The spiral configuration and relationship to the axis of the propagating structure 4 is shownin more detail in Fig. 2. Coupling means 16 is connected to spiral 19 in the region where spiral 19 is spaced the widest from planar surface 20 with the height of the spiral conductor 19 above surface 20 being such as to provide an impedance substantially equal'to the impedance present inv region 14 of the irst transition section 9. The low impedance propagating structure'S is coupled at spiral conductor- `19 in the region where spiral conductor 19 is spaced the least `amount from planar surface 20V and wherethe height of spiralr19 above` surface V2l) providesan impedance substantially equal to the characteristic impedance of the coaxial 4transmission line 5. Thus, through this arrangement, wave energy is coupled from coaxial transmission line 5 to propagating structure 4 in a reflectionless manner since the impedance of these two propagating structures are matched through cooperation to thc two transition sections 9 and 10.

The impedance match at the output end of propagating structure 4 between the'characteristic impedance of propagating structure 4 and the output coaxial line 6 is accomplished in substantially the same manner as illustrated -at the input' end of propagating structure 4, and

' thestructure thereof will not be discussed in detail heretion section 10 as shown lat 16.",It is to beunderstood A that, while Fig. l illustrates the coupling'between the two transition sections, to be an extension of helical conduct'or 12, this connection may be provided by a coaxial transmission line having a characteristic impedance substantially equal to theimpedance of the first transition section in the portion 14.V The second transition section 10 includes a disk 17 disposed coaxially of the lon,- gitudinal axis of propagating structure 4 and extending radially therefrom. As illustrated, disk 17 may bea portion of the magnetic pole piece energized byfmagnetic means 18 to aid in maintaining the electron beam at a substantially constant diameter as it passed through propagating structure 4. It is to be remembered, how.-Y ever, `that'disk 17 may be any disk Ydisposed in the Vinanner illustrated in Fig. l to behave as la groundlconductor. In spaced tapered relationship with Vrespect to a planar surface of disk 17 sdispOsed a spiral conductor 19, Vsuch that the'spiral` conductor v19 is in taperedspaced .relation'with the planar surface 20 of Ydisk V1'7. 'such that the widest spacingV between surface 20 and spiral 19,is

`'adjacent thevlongitudinal axis of propagating structure V4, and the narrowest Vspacing between spiral 19. and surface 20 is disposed along disk 17 removed from the longitudinal axis of propagating Vstructure 4. VI-twill be noted that spiral 179 is wound to occupy two planes in- V,tersercting at the axis of propagating Vstructure 4with these two Aplanes .being in aVV tapered relationwith the in, but reference may be had to the discussion of the inbeing identified by the same reference characters as employed for the impedance matching device but primed.

As illustrated in Fig. l, the spacing between spiral 19 and planar surface 20 is accomplished by employing a dielectric material 21 having the appropriate tapered configuration to provide the desired height of spiral 19 above surface'Z) along the radial dimension thereof. An appropriate material for this dielectric spacing is Teon.

As illustrated in Fig. l, the spiral 19 was spaced from the planar surface 20 facing toward the middle of the traveling wave tube. It is to be understood that spiral 19 may be spaced in tapered relationship from the other surface of disk 17 such that the spiral faces toward an end of the traveling wave tube. Such a configuration is illustrated in Fig. 3 wherein spiral 19 is spaced' in a tapered relationship from planar'surface 22 of disk 17. In this arrangement, it would be possible to dispose the magnetic means 18 closer to the axis of the propagating structure 4 and, hence, the size of the magnetic means 18 could be reduced since the magnetic field is now closer'to the axis wherein its etect must'be felt. The remainder of the impedance matching device is substantially identical with thatV illustrated in Fig. l, and the components are identified by identical reference characters. 'Y Y Y Employing the arrangement illustrated in Fig. 3, it is preferable to Vshield spiral 19 by means of an arrangement such as illustrated at 23 to prevent undesired radiation therefrom. This shielding arrangement 23 was not necessary in the conguration illustrated in Fig. l since the magnetic means 18 and cylinder 11, in effect, provide the desired shielding arrangement. f Referring to Fig. 4, there is illustrated another form which Vthe impedance matching device of this invention may take. lfhe first transition section 9 of the impedance matching device is` substantially identical as that illustrated in Fig. l, and reference characters as employed in Fig. l are shown Vin Fig. 4. The second transition section of the impedance matching device in ,accordance with this embodiment still employs a spiral in tapered relationship with a ground surface butV is structurally obtained in a dilerent manner. In accordance'with the embodiment illustrated in Fig. 4, the second transition section 10 is composed of arconducting cylinder 24 and a spiral conductor 2,5,disposed coaxially of and extending alongk the longitudinal axisr of cylinder 24V such that a tapered relation'ship exists between the inner surface 26 and the spiral conductor 25 substantially as illustrated. In this arrangement, the dielectric material between surface 26 and conductor 25 is air. As before, in connection with Fig. 1, the coupling means 16 is coupled to spiral conductor 25 and surface 26 in the region of transition section where the widest spacing occurs'between spiral 25 and the ground surface 26, while the low impedance transmission line 6 is coupled to spiral 25 and surface 26 in the region of the narrowest spacing between spiral 25 and ground surface 26. As in the coniiguration of Fig. 1, the points of coupling between the two transition sections is chosen so that the impedance of transition section 9 in the region 14 thereof equals the impedance of a transition section 10 at the point Where coupling means 16 is connected thereto.. Spiral 25 is mounted on a dielectric frusto conical member 27 which, in turn, may be mounted on a radially disposed disk member 23 which also serves to support cylinder 24 and, in eect, may be considered as part of the ground Surface. Disk 2S may be a portion of the magnetic circuit as discussed in connection with Fig. l or may be a separate radially extending component of the traveling wave tube or a separately applied component to carry out the impedance matching of this invention.

In the arrangement of Fig. l, it is contemplated that the input transmission line 5 will be brought in at one end of the traveling wave tube for connection to the input end 7 of the propagating structure 4, and the output transmission line 6 will be brought in at the other end of the traveling wave tube for connection to the output end 8 of the propagating structure 4. As is well known, there are certain advantages to having the input and output transmission lines brought in to the traveling wave tube at one end thereof. Such an arrangement is illustrated in Fig. 5 wherein input line 29 is brought in adjacent the output end of propagating structure 4, and the output line 3i), yas is the usual practice, is taken out at the output end of the propagating structure 4. The impedance match for this arrangement may be carried out as described herebefore in accordance with the principles of this invention and with certain modifications thereto hereinafter described. As described in connection with Fig. l, the impedance matching device is composed of two transition sections. The rst transition section is identical to that illustrated in Fig. l with the first transition section of the input impedance matching device being identified as 9 and the first transition section of the output impedance device being identified as 9. The portions of these iirst transition sections are identical to that illustrated in Fig. 1 and the corresponding reference characters are applied thereto in Fig. 5.

The second section of the input and output impedance vmatching devices are illustrated as being disposed at the output end of the propagating structure 4. The second section of the input impedance matching device is illustrated as including a spiral conductor 31, substantially identical in configuration and purpose as spiral 19 in Fig. l, spaced in tapered relationship with the planar surface 32 of disk 33. Both disk 33 and spiral 31 are disposed coaxially of the longitudinal axis of propagating structure 4 and extend radially therefrom. As in the embodiment of Fig. 1, the input coaxial line 29 has its outer conductor coupled to disk 33, and its inner conductor coupled to spiral 31 such that the impedance between spiral 31 and planar surface 32 equals the characteristic impedance of coaxial line 29. The impedance of this spaced spiral 31 and planar surface 32 increases to a value intermediate the low impedance of the coaxial line 29 and the high impedance of propagating structure d at a point adjacent the longitudinal axis of propagating structure 4. At this point, the coupling means 16 is coupled to the second transition section which, in this instance, is Yconstituted by coaxial transmission line which extends from thesecond transition section 10 to the first transiithe longitudinal axis of cylinder 36 match between 6 tion section 9 of' the input impedance l'natching` device, thereby connecting equal impedance points of transition sections 9 and 10.

The second section 10 of the output impedance matching device is disposed in spaced tapered relationship with planar surface 3S of disk 33 such that the impedance of output coaxial line 30 is matched to that of the characteristic impedance of propagating structure 4 in substantially the same manner as described in connection with section 10 of Fig. 5 of section 10 of Fig. 1. The coupling between the first and second transition sections 9 and iii', respectively, is accomplished by means of eX- tension of helical conductor 12 as indicated at 16.

Referring now to Fig. 6, there is disclosed therein an arrangement whereby the second transition section disclosed in Fig. 4 may be utilized in conjunction with a traveling wave tube wherein the input and output transmission lines are coupled to the traveling wave tube from the same end thereof. The first transition section of the impedance matching device is substantially identical to that described in connection with Fig. 1 and like reference characters for the first transition section will be employed herein. The second transition section 10 for the input impedance matching device in this instance is composed of a cylinder 36 and a spiral conductor 37 disposed coaxially of and extending along the longitudinal axis of cylinder 36 in tapered spaced relationship with the inner surface 38 of cylinder 36. -It will beobserved that the longitudinal axis of cylinder 36 is disposed at right angles to the longitudinal axis of propagating structure 4 to conserve on axial length. As described in connection with Fig. 4, the input transmission line 39 is coupled to spiral 37 at a point where the impedance of the second transition section 10 substantially equals the characteristic impedance of coaxial line 39 which occurs in the region of the narrowest spacing between spiral 37 and ground surface 38. Transition section 10 is then coupled to transition section 9 by coupling means 16 which, -in this instance, takes the form of a coaxial transmission line 40 to couple equal impedance points of transition sections 9 Vand 10 together. Y

The second transitionsection 10' of the output impedance matching device has substantially the same configuration as .the transition section 10 of the inputrir'npedance device of Fig. 6 andalso is disposed toV have at right angles to the longitudinal Iaxis of propagating structure 4.. The coupling between transition sections 1G and 9 is accomplishedpin this instance .as illustrated in Fig. 6 by transmission line 41 of a characteristic impedance equal substantially to the impedance of transition section 10 rand transition section 9 at the point of coupling 'together.

It is .to beAunderstood, however, that an extenl'sion of helical conductor 12 may also be used i-f warranted to accomplish the coupling between the two tran- -sition sections of the .impedance matching device.

Herein-above there has been discussed variations of an impedance matching `device lcomprising two impedance transition sections cooperating together to provide the desired impedance match between a low impedance coaxial transmission line and a relatively high impedance helical propagating structure. It vis ,to be remembered that in certain instances each of the .transition sections may be employed separately to provide the desired impedance matching. However, in certain -instances, the sections individually will not provide the desired impedance match and, therefore, must be used in the cooperative arrangement discussed hereinabove. It should be further pointed out that it is the spacing between the spiral conductor and the conducting ground surface in transition section 10' and the spacing between the lconducting `ground cylinder 11, and the helical conductor y12 which provides the change of impedance to enable the accomplishing of the impedance the relatively low impedancecoaxial transmission line and the relatively high impedance helical propagating structure of the Vtraveling wave tube.

' That is, it is the height of a -line conductor above a where his equal to the spacing between the ground surface and the conductor, `and d is equal to the diameter of the conductor and e is equal to the dielectric coni `stant, of the dielectric material disposed between the conductor l and-the ground surface.

'While I have described above the principles of `my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of vexample and not as a limitation to the scope of my invention as set [forth in the objects thereof and in the accompanying claims.

I claim:V n

l. A broadband radio |`frequency impedance matching device for use between a |wave energy propagating Aline having a relatively -low characteristic impedance and a wave energypropagating line having a relatively high characteristic impedance comprising in combination rst and second impedance transition sections, and means coupling equal impedance points of said first and second transition sections to each other, said rst transition section including a first line-above-ground transmission line having a conducting cylinder and a helical conductor disposed within and coaxially of said cylinder, the spacing between said conducting cylinder and said helical conductor being tapered from a narrow spacing to a relatively wide spacing, and said second transition section including a. 'second line-.above-ground transmission line having ,-rst and second conductors, said sec ond conductor hav-ing a substantially constant pitch spiral conguration, said rst and second conductors being dis.- posed lin la tapered spaced relationship with respect to each other, said second transition section including a conductive disk disposed coaxially'of and extending radially from a Vgiven axis and a conductive spiral disposed coaxially of said given axis and in tapered spaced relationship with respect to one of the'planar surfaces of saidV disk to provide said second Iline-above-ground t-ransmission'line. i

2.Y A device `according to claim 1, wherein the spacing of said spiral and said planar surface is tapered from a wide spacing adjacent said -given axis to -a narrow spacing removed-from said lgiven axis.

3. A device according to claim 2, wherein said low impedance line is coupled to said second transition section at a point removed trom said given axisfhaving an Vimpedance equal to4 its'characteristicv impedance and said couplingrmeans is coupled to said second transition section at a point adjacent to said `given axis having an impedance equal to the impedance of the narrow 'spacing of said irst transition' section. t

4. A device according to claim 3, wherein said high .impedance line is vcoupled to the point of wide spacing in said first transition section. Y U

5. A' broadband radio frequency impedance matching device tor use between a wave energy propagating line having a relatively low characteristic impedance and a. waveenergy propagating line having a relatively high characteristic impedance comprising in combination tirst and second impedance transition sections, and means coupling equal impedance points of said rst and second ,transition sections to eachother, said iirst transition section including a first line-above-ground transmission line having a conducting cylinder and a helical conductordisposed within and coaxially of said cylinder,` the spacing between said conducting cylinder and Vsaid helical conductor. being tapered from a narrow spacing to aV relatively wide spacing, and said second, transition section including "a second line-above-ground transmission line'having first and second conductors, said sec-l ond conductor having a substantially constant pitch spiral conguration, said first and second conductors being disposed in a tapered spaced relationship with respect to each other, said second transition section including a conductive cylinder having its longitudinal axis parallel to the longitudinal axis of said high impedance line and a conductive spiral disposed coaxially of and extending along the longitudinal axis of said conductive cylinder in tapered spaced relationship with a surface of said conductive cylinder to provide said secondV line-above` ground transmission line.

6. A device according to claim 5, wherein said spiral is disposed within's'aid conductive cylinder and in tapered spaced relationship with the inner surface of said conductive cylinder.

7. A device according to claim 6, wherein said low impedance line is coupled to said second transition section in the region of narrow spacing between said spinal and said conductive cylinder having an impedance equal to its characteristic impedance Iand said coupling rneans is coupledto said second transition section in the region of wide spacing between Vsaid'spiral and said conductive cylinder having an impedance equal to the impedance of the narrow spacing of said irst transition section.

8. A device according to claim 7, wherein said high imeda-nce line is coupled to the point of wide spacing in said lirst transition section. Y

9. A broadband radio frequency impedance matching device for use between a relatively low impedance wave energy propagating line and a relatively high impedance Wave energy propagating line comprising a transition section including a linefabove-ground transmission line having a spiralconductor and a ground conductor, said spiral conductor Vhaving a substantially constant pitch, said spiral conductor and said ground conductorybeing disposed in :a tapered spaced relationship with respect to each other, said high impedance line being coupled to said conductors in the region of the widest spacing thereof and Vsaid low impedance line being coupled to said conductors in the region of the narrowest spacing thereof, said transition section including a conductive disk disposed coaxially of and extending radially from a given axis and a conductive spiral disposed coaxially vof said givenV axis and in tapered spaced relationship with respect to one of lthe planar surfaces of said disk to provide said line-above-ground transmission line.

l0. A device according to claim 9, wherein the spacing of said spiral and said planar surface Vis tapered from a wide spacing `adjacent said given axis to a narrow spacing removed from said given axis.

11. A broadband radio frequency impedance matchingrdevice for use between a relatively low 'impedance wave energy propagating line and a relatively high irnpedance wave energy propagating line comprising a transition section including a line-aboveeground transmission line having a spiral conductor and-a ground conductor, 'saidspira'lfconducton having a Vsubstantially constant pitch, said spiral conductor and said ground conductor being disposed in a tapered spaced relationship with respect to each other, said high impedance line being coupled to said conductors in the region of the widest spacing thereof and said lowimpedance line being coupled toV said conductors in the region of thenarrowest spacing thereof, said transition section including la conductive cylinder having its longitudinal axis parallel tothe longitudinal axis of said high impedance line and a conductive spiral disposed coaxially of and extending along the longitudinal axis of said conductive cylinder in tapered spaced relationship with lasurfacerof'said conductive cylinder `to provide said line-above-ground transmission line. i

12. A device according to claim l1, wherein said spiral is disposed within said conductive cylinder and in tapered spaced relationship with the inner surface of said conductive cylinder.

13. In a traveling wave electron discharge device having :a collector electrode, means to project lan electron beam along a given path to said collector electrode, a helical wave energy propagating structure disposed in interacting relation with the electrons of said electron beam, and input and output coaxial transmission lines for said helical structure, an input and output broadband radio frequency impedance .matching device for matching the characteristic impedance of said helical structure to the characteristic impedance of said input and output coaxial transmission lines, each of said impedance matching devices comprising a iirst transition section including a tirst line-above-ground transmission line having la conducting cylinder coaxially of the axis of said helical structure and a helical conductor disposed coextensive with, within and coaxially of said cylinder coupled to the appropriate end of said helical structure7 the spacing between said conducting cylinder and said helical conductor being tapered from a relatively wide spacing adjacent the end of said helical structure to a relatively narrow spacing removed from the end of said yhelical conductor, a second transition section including la second line-above-ground transmission line having iirst and second conductors coupled to said coaxial transmission line, said second conductor having a substantially constant pitch spiral coniiguration, said -lirst and second conductors being disposed in a tapered spaced relationship with respect to each other from a relatively narrow spacing adjacent said coaxial transmission line to a relatively wide spacing, and means coupling said secondtransition section in the wide spacing region thereof to said -rst transition section in the narrow spacing region thereof, said input and output coaxial transmission lines being disposed at opposite ends of said helical structure, said second transition section of each of said'impedance matching devices including a yconductive disk disposed coaxially of and extending radially from the axis of said helical structure adjacent the appropriate end thereof and a conductive spiral disposed coaxially of the axis of said helical structure and in tapered spaced relationshipv with respect to one of the planar surfaces of said disk to provide said second line-above-ground transmission line, the widest spacing between said spiral and said disk being disposed adjacent the axis of said helical structure and said coupling means includes an extension of said helical conductor.

14. In a traveling wave electron discharge device Ahaving a collector electrode, means to project an electron beam along a given path to said collector electrode, a

helical wave energy propagating structure disposed in interacting relation with the electrons of said electron beam, and input and output coaxial transmission lines' for said helical structure, an input and output broadband radio frequency impedance matching device for matching the characteristic impedance of said helical structure to the characteristic impedance of said inp'ut and output coaxial transmission lines, each of said impedance matching devices comprising .a iirst transition ysection including a rst line-above-*ground transmission line having a conducting cylinder coaxially of the axis of said helical structure and a helical conductor disposed coextensive with, within and coaxially of said cylinder coupled to the appropriate end of said helical structure, the spacing between said conducting cylinder and said helical conductor being tapered from a relatively wide spacing adjacent the end of said helical structure to a relatively narrow spacing removed from the end of said helical conductor, a second transition section including a second line-aboveground transmission line having first and second conductors ycoupled -to said coaxial'transmission line, said second conductor having a substantially `constant pitch spiral configuration, said iir'stv and second conductors being disposed ina tapered spaced relationship with respect to each other from a relatively narrow spacing adjacent said coaxial transmission line to a relatively wide spacing, and means coupling .said section transition section in the wide spacing region thereof vto said first transition section in the vnarrow spacing region thereof, said input and output coaxial transmission lines being disposed at opposite ends of said helical structure, said second transition section of eachrof said impedance matching devices including a conductive cylinder having its longitudinal axis parallel to the axis of said helical structure disposed adjacent the appropriate end thereof and a conductive spiral disposed within, coaxially of and extending along the longitudinal axis of said conductive cylinder in tapered spaced relationship `with .the inner surface of said conductive cylinder to provide said second line-above-ground transmission line and said coupling means includes an extension of said helical conductor.

j l5. In a traveling wave electron discharge device having a collector electrode, means to project an electron beam yalong a lgiven path to said collectoi` electrode, a helical wave energy propagating structure disposed in interacting relation with the electrons of said electron beam, and input and output coaxial transmission lines for-said helical structure, an input and output broadband radio frequency impedance matching device for matching the characteristicimpedance of said helical structure to the characteristic impedance of said input and output coaxial transmissionlines, each of said impedance matching devices comprising a first .transition section including a first line-above-ground transmission line having a conducting cylinder lcoaxially of the axis of said helicalstructure and a helical conductor disposed coextensive with, within and coaxially of said cylinder coupled to the appropriate end of said helical structure, the spacing between said conducting cylinder and said helical conductor being tapered from a relatively wide spacing adjacent thewend of said helical structure to a relatively narrow spacing removed from the end of said helical conductor, a second transition section including a second line-aboveground transmission line having lirst and second conductors coupled to said coaxial transmission line, said second conductor having a ysubstantially constant p itch spiral configuration, said irst and second conductors being dis- 'posed in a tapered spaced relationship with respect to each other from a relatively narrow spacing adjacent said co'- axial transmission line to a relativelyv wide spacing, and means coupling said transition section in the wide spacing region thereof to said iirst transition section in the narrow spacing region thereof, said input and -output coaxial transmission lines being both disposed adjacent the output end of said helical structure, said second transition section -of lsaid Ainput impedance matching device including a conductive disk disposed coaxially of and extending radially from the axis Vof said helical structure adjacent the output end thereof `and a first conductive spiral disposed coaxially of the axis of said helical structure and in tapered spaced relationship vwith respect to one of the planar surfaces of said vdisk to provide said second line-above-ground transmission line of said input impedance vmatching device, the -Widestspacing between said lirst spiral and said one planar surface being disposed adjacent the axis of said helical structure and said means coupling includes a coaxial transmission line extending to the' .input end of said propagating structure and said second transition section of said output impedance matching device including a second conductive spiralrdisposed 'coaxially of the axis of said helical structure andv in tapered 'spaced relationship with respect to the other of the planar surfaces of said disk to provide said second line-aboveground transmission line of said output impedance matching device, 'the widest spacing between said second spiral and said other planar' surface 'being disposed adjacent the 1l axis of said Ahelical structure andrsaid meansk coupling includes an extension of said helical conductor of said ,rst transition section of said output impedance matching device. Y t j 16. In a traveling wave electron'discharge devicei having a collector electrode, ineans Vto project an electron beam along a given path to said collector electrode, a helical wave energy propagating structure disposed in interacting relation with the electrons of said electron beam, and inputV and output coaxial transmission lines for said helical structure, 'an input and output 'broadband radio frequency impedanceY matching device for matching the characteristicimpedance of saidlhelical structure to the characteristic impedance of said input and out-puticoaxiai transmission lines, each of saidA impedance matching devices comprising-a iirst transition section including a irst line-above-ground transmission lineihaving a conducting cylinder coaxially of the vaxis ofrsaid helical'stnucture and a helical conductor disposed coextensive with, within and coaxially of said cylinder coupled to the appropriate end of said helical structure, therspacing between said conducting cylinder and said helical conductor being tapered from a relatively wide spacing adjacent the end of Said helical structure to a relatively narrow spacing removed from the'end of said helical conductor, a second transition section includingya second line-above-ground transmission line having first and second conductors coupled to said coaxialV transmission line, said second conductor having a substantially constant pitch spiral configuration, said-first andsecond conductors being disposed in a tapered spaced relationship Ywith respect to each other from a relatively narrow spacing Iadjacent said coaxial transmission line -to a relatively Wide spacing, andV means coupling said second'transition section in the wide spacing regiontliereof to said iirst transition section inthe narrow spacing region thereof, said input and output coaxial transmission lines being 'both disposed adjacent the output endofsaid helical structure, said second transi- .tion -section ofsaid input "andoutput impedance matching device each include a Vconductive cylinder having its longitudinal axis perpendicular to the axis of said helical structure disposed adjacent the output end thereof and a conductive-spiral disposed within,` coaxially of and extendingalong the longitudinal axis of Vsaid conductive p cylinder in tapered spaced relationship with the inner surface ofjsaid vconductive cylinder to vprovide said second line-above-ground Vtransmission line and said coupling means Aincludes acoaxial'transmission line extending to said rst section of the corresponding impedance matching device. Y

17. A broadband radio frequencyimpedance matching device for use between a wave energy propagating line having a relatively low 'characteristic impedance and a wave'energy propagatingrline having Varrelatively high characteristic impedance VVcomprising in vcombination Iirst and second impedance transition sections, and means coupling equal impedance points'of said first and second transition sections to each other, said'iirst'transition sec'- tion including a Erst line-above-ground transmission line having a conducting cylinder and a helical conductor disposed within and coaxially of said'cylinden the spacing between said conducting cylinder and said helical convductor being tapered from a narrow spacing to arelatively wide spacing, and saidV second transition section including a second line-above-ground transmission line, afconductive disk disposed coaxially of and extending radially from a given axis andra conductive spiral disposed coaxially of saidY given axis and in tapered spaced relationshipV with respect to one of the planar surfaces of said disk.

A L8. A device according to claim 17, wherein the spacing wide spacing adjacent said given removed from said given axis.; t

impdance, lisais ccunledtdsaid; second transition section of said spiral and said planar surface isV tapered froma at Ta point removed from said given axis -having an mpedance equal to the characteristic impedance of said low impedance line ands'aidA coupling means is coupledtto said second transition section at a given point adjacent to said given axis having an impedance equal to the impedance of the narrow spacing of said iirst transition section.` i

20. A device according to claim 19, wherein said high impedance line is coupled to the point of wide spacing in said iirst transition section. Y

V42l. A broadband radio frequency impedance matching device for use between a relatively low impedance wave' energy propagating line and a relatively high ini-j pedance wave energy propagating line comprising a transition section including a line-above-ground transmission line having a spiral conductor and a ground conductor disposed in tapered spaced relation, said high impedance line being coupled Vto said conductors in the region of the widest spacing thereof and said low impedance line being coupled to said conductors in the region of the narrowest spacing thereof, said transition section including a conductive Vdisk disposed coaxially of and extending radially from a given axis and a conductive spiral disposed coaxiallyof said given axis and in tapered spaced relationship with respect to one of the planar surfaces of said disk toprovide said line-above-ground transmission line.

22. A device according to claim 21, wherein the spacing of said spiralrand said planar surface is tapered from a wide spacing adjacent said given axis to a narrow spacing removed from said given axis.

23. In astraveling wave electron discharge device having a collectorl electrode, means to project an electron beam along a given path to said collector electrode, a helical wave energy propagating structure disposed in interacting relation with the electrons of said electron beam, and input and output coaxial transmission lines for said helical structure, an input and output broadband radio frequency impedance matching device for matching the characteristic impedance of said helical structure to the characteristic impedance of said input and output coaxial transmission lines, each of said impedance matching devices comprising a first transition section including a tirst line-above-ground transmission line having a conducting cylinder coaxially of the axis of said helical structure and a helical'conductor disposed coextensive with, within and coaxially of said cylinder coupled to the appropriate end of said helical structure, the spacing between said conducting cylinder and said helical com ductor-being tapered from a relatively wide spacing adjacent the lend of said helical structure to a relatively narrow spacing removed vfrom the end of said helical conductor, a second transition section including a second line-above-ground transmission line, first and second conductors coupled to said coaxial transmission line, the spacing between said first and second conductors being tapered from a relatively narrow spacing adjacent said .coaxial transmission-line to a relatively wide spacing,

and means coupling said second transition section in the wide spacing region thereof to said first transition section 4in the narrow spacing region thereof, said input and output coaxialtransmission lines being disposed at opposite ends of said helical structure, said second transition sec-V tion of each of said impedance matching device including a conductive disk disposedcoaxially of and extending radially from the axis Voftsaid helical structure adjacent the appropriate end thereof and a conductivey spiral disposed coaxially of the axis of saidthelical structure and in tapered spaced relationship with respect to Vone of the planar surfaces of said disk to provide said second lineabove-ground transmission line,ithe widest spacing between said spiral and said disk being disposed adjacent the axis'of said helical structure andV said coupling means includes an extension of said helical conductor. Y Y 24.lna traveling wave electrondischarge device having va@collector electrode, means to projectan electron beam along a given path to said collector electrode, a helical wave energy propagating structure disposed in interacting relation with the electrons of said electron beam, and input and output coaxial transmission lines for said helical structure, an input and output broadband radio frequency impedance matching device for matching the characteristic impedance of said helical structure to the characteristic impedance of said input and output coaxial tranmission lines, each of said impedance matching devices comprising a first transition section including a iirst line-above-ground transmission line having a conducting cylinder coaxially of the axis of said helical structure and a nelical conductor disposed coextensive with, within and coaxially of said cylinder coupled to the appropriate end of said helical structure, the spacing between said conducting cylinder and said helical conductor being tapered from a relatively wide spacing adjacent the end of said helical structure to a relatively narrow spacing removed from the end of said helical conductor, a second transition section including a second line-aboveground transmission line having irst and second conductors coupled to said coaxial transmission line, the spacing between said iirst and second conductors being tapered from a relatively narrow spacing adjacent said coaxial transmission line to a relatively wide spacing, and means coupling said second transition section in the wide spacing region thereof to said rst transition section in the narrow spacing region thereof, said input and output coaxial transmission lines being both disposed adjacent the output end of said helical structure, said second transition section of said input impedance matching device including a conductive disk disposed coaxially of and extending radially from the axis of said helical structure adjacent the output end thereof and a first conductive spiral disposed coaxially of the axis of said helical structure and in tapered spaced relationship with respect to one of the planar surfaces of said disk to provide said second line-above-ground transmission line for said input impedance matching device, the widest spacing between said rst spiral and said one planar surface being disposed adjacent the axis of said helical structure and said means coupling includes a coaxial transmission line extending to the input end of said propagating structure and said second transition section of said output impedance matching device including a second conductive spiral disposed coaxially of the axis of said helical structure and in tapered spaced relationship with respect to the other of the planar surfaces of said disk to provide said second line-above-ground transmission line for said output impedance matching device, the widest spacing between said second spiral and said other planar surface being disposed adjacent the axis of said helical structure and said means coupling includes an extension of said helical conductor of said first transition section of said output impedance matching device.

References Cited in the file of this patent UNITED STATES PATENTS 2,578,434 Lindenblad Dec. 11, 1951 2,712,614 Field July 5, 1955 2,727,179 Lally et al. Dec. 13, 1955 2,789,246 Wang Apr. 16, 1957 2,803,777 Bryant Aug. 20, 1957 2,848,645 McBee Aug. 19, 1958 2,849,651 Robertson Aug. 26, 1958 FOREIGN PATENTS 1,139,162 France Feb. 4, 1957 

